Synthesis and evaluation of small molecule based reactive oxygen species ros generators

Abstract

Nearly all aerobic organisms use oxygen for respiration Electrons released during respiration from redox enzymes are accidentally abstracted by O2 to produce superoxide O2 9679 8211 which is subsequently converted to hydrogen peroxide H2O2 In the presence of trace metal ions such as Fe2 or Cu H2O2 can produce the highly reactive hydroxyl radical OH 9679 Together these species can react with the majority of biomacromolecules such as DNA proteins and lipids causing oxidative damage and are hence called reactive oxygen species ROS It is therefore not surprising that ROS are generated in immune cells to combat invading pathogens as a protective mechanism Recently ROS have been shown to sensitize infectious pathogens to clinical antibiotics suggesting that ROS generating drugs could be used as antibacterials With the rapid rise in bacteria acquiring drug resistance to most commercial antibiotics development of new interventional strategies to help overcome drug resistance is critical This however requires developing methodologies for the controlled generation of ROS Although there are few methods available none of them are suited for reliable ROS generation Here three distinct approaches for controlled ROS generation will be presented First a series of dihydrobenzoquinones were evaluated as sources of O2 9679 8211 in physiological pH These compounds are expected to undergo an enolization in buffer to produce a 1 4 dihydroxyarene which are known to react with oxygen to generate ROS In this series ROS generation was found to depend in part on the propensity of the 8220 keto 8221 form of the dihydrobenzoquinone to enolize thus providing a structural handle to regulate rates of ROS generation Having established the utility of these compounds to generate ROS in cell free systems we investigated the ability of these compounds to permeate cells to elevate ROS Using an array of techniques we provide evidence for these compounds to enhance ROS in bacteria including mycobacteria We next exploited the utility of the